1. Field of the Invention
This invention relates to packaging processes; particularly those pertaining to packing of items having sharp protrusions and those pertaining to packing of edible products. Additionally, this invention relates to foamed polymeric materials suitable for use in such processes and compounds useful in the production of such foamed materials.
2. Description of the Relevant Art
In a variety of areas it is necessary to package products in such a manner as to cushion sharp protrusions or particularly fragile portions. This is particularly necessary in food industries such as meat packing where products are wrapped in air-tight polymeric films.
When animal carcasses are prepared for shipping, they are often subdivided into portions and individually wrapped in an outer wrapper for preservation and protection during shipping and handling. The preferred outer wrap is an air-tight polymeric material in which the cut of meat may be vacuum packed and sealed. The size of the cuts of meat vary from smaller consumer-sized portions to very large "primal cuts" weighing many pounds.
Most meat portions are irregularly shaped and contain bones which protrude at one or more places on the cut. The protrusions which can be relatively sharp, tear and pierce the outer polymeric wrap in which the meat is encased. During storage and shipment from packing plant to warehouse, retailer or user, the cut is handled several times; further increasing the chances of puncture or tearing of the outer wrap. This is particularly possible at the points of contact between the bag and the protruding bone. Vacuum packaging to increase storage life also increases the risk of the outer wrap tearing. In vacuum packaging, the wrap is forced to conform to the contours of the meat during the evacuation process. This can cause stretching and strain over the protruding areas.
Various approaches have been tried to overcome the problems associated with torn or leaking outer wrappers. For example, the outer wrapper material may be strengthened to resist puncture. This would entail modification to the content or thickness uniformly throughout the wrapper which would be expensive and unnecessary in view of the fact that the areas likely to be punctured are relatively limited.
Specialized containers have been proposed such as the one disclosed in U.S. Pat. No. 4,136,205 to Quattlebaum. Such containers are generally reinforced with suitable cloth or strengthening material at points in the bag which roughly correspond to the protrusions. These containers are relatively expensive and require accurate placement of the meat cut within them if they are to function satisfactorily. Many configuration of these type of containers in many sizes may be necessary to package different cuts of meat as the various cuts have different contours and protrusions. Additionally, the carcasses of a particular type of animal may vary greatly in size and weight.
Currently, the common practice in the meat packing industry is to swath the cut in a large piece of a wax-impregnated, non-absorptive fabric prior to insertion in the outer wrapper. The fabric is interposed between the wrapper and the meat at puncture prone areas such as bone ends. Examples of such material are found in U.S. Pat. Nos. 2,891,870 and 3,653,927. In order to insure that the protrusions are adequately covered during insertion in the outer wrap, large amounts of the fabric must be used covering major portions of the meat cut. This process is laborious time-consuming, expensive and generates a great deal of waste material and labor when the wrap is removed.
Because of these drawbacks, other methods of cushioning sharp protrusions have been proposed. Attempts have been made to cushion meat cuts in a variety of preformed foam materials positioned between the meat and wrapper. As indicated in U.S. Pat. No. 4,136,203 to Murphy, generally these attempts have not been satisfactory due to discoloration of meat in contact with the foam caused by residual oxygen present in the foam. In order to overcome this problem, the Murphy reference proposes the use of an oxygen impervious wrapper film between the meat and foam. Additionally, the mass of the foam and wrapper employed in Murphy created transportation problems; adding weight and volume to each carcass and increasing transport costs, clearly, this solution does not promote packing efficiency or economy.
Direct application of cushioning materials, either foamed or non-foamed, to the meat has met with several drawbacks. Heretofore, all materials available had to be applied at a temperature so high as to cause scalding and discoloration of the meat. In addition, many known cushioning materials were inappropriate for use with edible products. Others did not set rapidly enough to provide complete coverage.
Thus, it is desirable to provide a process for packaging products, particularly edible products such as meat, which reduces the chance of package rupture. It is desirable that this process employ a polymeric material which can be easily and selectively applied to protrusions without causing discoloration or blemishing of the meat. It is also desirable to provide a process in which a foamed material can be produced at the use site and dispatched at low temperatures. Finally, it is desirable to produce a foamed polymeric material which can be employed in a variety of packaging and other applications.